In general, the washing machine is a home appliance for removing dirt from laundry by using chemical decomposition and mechanical impact.
There are drum type and pulsator type in the washing machines. It is recent trend that demand for the drum type washing machines increases gradually because the drum type washing machine enables to reduce an overall height of the washing machine, increase washing capacity, reduce washing water, and cause almost no problem of laundry entangle, and the like, compared to the pulsator type washing machine in which a drum rotates in an upstanding position.
A related art drum type washing machine will be described with reference to the attached drawings.
FIG. 1 illustrates a section of a related art drum type washing machine, provided with a cabinet 10 forming an exterior, a tub 20 in the cabinet 10, a damper 100 and suspension springs 50 for supporting the tub, a substantially cylindrical drum 30 rotatably mounted in the tub 20, and a driving unit 40 serving as a driving source for driving the drum 30.
In general, the driving unit 40 is provided with a stator mounted to a rear wall of the tub, and a rotor mounted on an outside of the stator and directly coupled to the drum with a shaft for rotating when power is applied to the stator, of which detailed description will be omitted.
The suspension springs 50 are mounted between an upper surface of the cabinet 10 and an upper portion of the tub 20, and the damper 100 is mounted between a base of the cabinet 10 and the lower portion of the tub 20, for damping vibration of the tub 20 occurred at the time of spinning.
The operation of the related art drum type washing machine will be described.
When the user intends to wash laundry, upon pushing a washing start button after putting in the laundry in the drum 30 in a state power is applied thereto, washing water is supplied to the drum 30.
Upon finishing water supply, the drum 30 rotates by driving force of the driving unit 40 in a state the laundry is submerged in the washing water.
As the drum 30 rotates, the laundry and water in the drum 30 are lifted upward to a predetermined height following an inside surface of the drum 30, and fall down, to cause impact and friction coming from a head to the laundry as above steps are repeated, such that the washing is made by the impact and friction and decomposition by detergent.
Upon finishing the washing, a spinning step is started after passing through a rinsing step according to a number of times set at a microcomputer. In the spinning step, the drum 30 rotates at a high speed, for extracting water.
The drum type washing machine in FIG. 1 illustrates one without a drying function. There is a drum type washing machine which can drying after spinning.
In the meantime, as dampers for damping vibration of the tub 20 during washing and spinning of the drum type washing machine, there are a friction damper for performing damping by friction force, and an oil damper utilizing fluidity of oil. Though the oil damper is favorable in view of damping characteristics, since the friction damper is favorable in view of price, the friction damper is used widely.
That is, because the price of the oil damper is higher than the friction damper by more than five times, the manufacturer is required to take a burden of excessively high production cost of the drum type washing machine if the oil damper is used.
FIG. 2 illustrates a perspective view of an exterior of a related art oil damper D′.
Referring to FIG. 2, the related art oil damper D′ is provided with a metal cylinder 1a with metal caps 60 welded to opposite ends respectively, oil filled in the cylinder 1a, a shaft 70 exposed through one end thereof, and a metal piston (not shown) coupled to the other end wherefrom the shaft 70 is not exposed to an outside of the metal cylinder 1a, so that the piston slides inside of the metal cylinder.
Accordingly, the related art oil damper D′ has many disadvantages in application to a product, due to high the production cost, and low productivity coming from requirement for a welding step because the related art oil damper D′ is constructed of metal entirely, and a high sliding resistance of the piston during operation of the oil damper D′ which causes a problem of reliability in operation.